This invention relates to the field of computer systems. More particularly, a system and methods are provided for calculating headroom margin.
Computer systems become less responsive as utilization of their resources (e.g., processors, disk drives, memory, communications) approaches 100%. At a given level or percentage of utilization, the remaining capacity of a particular device or set of devices comprises usable headroom plus margin. Headroom comprises capacity that may still be allocated. Margin comprises capacity that should not be used, so as to maintain adequate response time.
The minimum size of the margin depends on many factors, such as utilization, workload characteristics, the number of devices servicing the workload, how acceptable a decrease in performance or response time is, etc. However, no adequate methods of calculating an effective or desirable margin presently exist that can consider the various pertinent factors. As a result, capacity planning becomes very difficult, particularly for environment in which workloads vary.